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From "Ashutosh Chauhan (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-8625) Some union queries result in plans with many unions with CBO on
Date Wed, 29 Oct 2014 18:18:34 GMT

    [ https://issues.apache.org/jira/browse/HIVE-8625?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14188730#comment-14188730
] 

Ashutosh Chauhan commented on HIVE-8625:
----------------------------------------

Committed to trunk.

> Some union queries result in plans with many unions with CBO on
> ---------------------------------------------------------------
>
>                 Key: HIVE-8625
>                 URL: https://issues.apache.org/jira/browse/HIVE-8625
>             Project: Hive
>          Issue Type: Bug
>          Components: CBO
>    Affects Versions: 0.14.0
>            Reporter: Jesús Camacho Rodríguez
>            Priority: Minor
>             Fix For: 0.15.0
>
>         Attachments: HIVE-8625.patch
>
>
> For some queries e.g. union9, union16, we are getting plans with many binary unions when
CBO is on. The reason is that an identity select operator is introduced after each union by
the CBO; thus, the method that was merging the unions when the translation of the AST into
a logical plan was being done is not executed, as it does not detect there is another union
operator. 
> With the fix in the patch attached, the method will merge the two unions if (1) one is
the child of the other one, or (2) if one is a descendant of the other one and there is an
identity select operator between them.



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